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The development and validation of the Epilepsy and Learning Disability Quality

of Life (ELDQOL) scale

Deborah Buck1, Monica Smith1, Richard Appleton2, Gus A Baker3, Ann Jacoby4

1 Institute of Society and Health, Newcastle University, UK2 Alder Hey Children’s Hospital, Liverpool, UK3 The Walton Centre for Neurology and Neurosurgery, Liverpool, UK4 Dept of Public Health, University of Liverpool, UK

Corresponding author:

Professor Ann Jacoby

Dept of Public Health

Whelan Building

University of Liverpool

Brownlow Hill

Liverpool

UK

Phone: +44 (0) 151 794 5602

Fax: +44 (0) 151 794 5588

Email: ajacoby@liverpool.ac.uk

Word count: 2,646 (excluding tables and references)

Keywords: epilepsy, children, learning disabilities, quality of life, carer, assessment

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Abstract

Few suitable instruments exist for use with people, especially children, with both

epilepsy and learning disabilities. One such measure is the Epilepsy and Learning

Disabilities Quality of Life scale (ELDQOL), which has recently undergone revision

following feedback from relevant users. This paper reports on the final psychometric

testing phase of ELDQOL. ELDQOL consists of 70 items covering seizure severity,

seizure-related injuries, AED side-effects, behaviour, mood, physical, cognitive and

social functioning, parental concern, communication, overall QOL and overall health.

Revalidation involved a qualitative phase to ascertain users’ opinions on the wording,

coverage and layout of the questionnaire; and a quantitative phase to examine internal

consistency and test-retest reliability, and validity. The final version of ELDQOL has

very good evidence of reliability and validity, making it a promising instrument for

assessing QOL in children/young adults with epilepsy and learning disability.

Word Count: 138

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Introduction

There is general agreement within the health outcomes field of the importance of

assessing therapeutic outcomes including quality of life (QOL).1 Medical

interventions may be beneficial to patients on impairment or disability measures, but

without equally refined QOL measurements a clear and comprehensive evaluation of

their efficacy is not possible.2,3 The assessment of QOL in adults with epilepsy is now

widespread with the existence of a number of psychometrically sound measures.4

However, reviews of outcome measures have shown that few suitable instruments

currently exist for use with people who have both epilepsy and learning disabilities.1,5

One recently developed measure, the Epilepsy Outcome Scale (EOS),6 was developed

to be completed by carers of people with epilepsy and learning disabilities (LD), but

while valid and reliable, it is intended for adults rather than children with these

conditions. A recent review of QOL measures for use specifically with children and

adolescents with epilepsy1 identified five epilepsy-specific instruments, of which three

were considered potentially suitable for children who had LD: the Health-related

Quality of Life in Children with Epilepsy measure; 7 the Impact of Childhood

Neurological Disability Scale (ICND); 8 and the Epilepsy and Learning Disabilities

Quality of Life scale (ELDQOL).9-12

The Health-related Quality of Life in Children with Epilepsy measure was not

purposely developed for those with both epilepsy and LD. However, it does

incorporate a self-report (completed by the child) as well as a proxy-report which can

be completed by parents alongside or instead of the child report, and seems to be

reasonably valid and reliable.1 The ICND assesses the impact of epilepsy and

concomitant behavioural, cognitive, and physical/neurological disability in children. It

has good reliability and is reported to be satisfactory in terms of validity.1

ELDQOL is specifically aimed at informal/formal carers of children with both severe

epilepsy and LD. Initial evidence of its psychometric properties was reported by the

scale’s developers13, and subsequently ELDQOL was reviewed by Espie et al5 who

also reported evidence of internal and test-retest reliability, and some evidence of

sensitivity. ELDQOL has been used in two studies, results of which have been

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reported.11,14

However, as a result of feedback from clinicians involved, it was decided to undertake

revision and revalidation of ELDQOL. This paper reports on the psychometric testing

of the final, revised version of ELDQOL. A detailed report of the earlier stages in its

development is available from one of the authors (AJ). A summary of its history will

be provided here.

Initial development of ELDQOL

Potential items for inclusion in the pilot structured measure were selected based on in-

depth interviews with parents of children with severe epilepsy. The measure was then

piloted to assess its psychometric properties (content and construct validity, internal

consistency and test-retest reliability) and acceptability to parents. Parents of 50

patients across 5 UK paediatric neurology out-patient departments were recruited to

the pilot study.

The pilot version of ELDQOL consisted of 66 items across 6 domains: seizure

severity, seizure-related injuries, AED side-effects, behaviour, mood and overall QOL.

It was found to be satisfactory in terms of content and construct validity and internal

consistency, and showed high test-retest reliability. Furthermore, parents commented

that the measure was comprehensive, relevant and easy to complete. The pilot version

of ELDQOL was subsequently used in a clinical trial of Lamictal11 which provided

evidence of its responsiveness. However, a number of criticisms were made about the

measure by clinicians involved in the trials, particularly in terms of the clarity of

meaning of several items and of the appropriateness or sensitivity of response sets.

Consequently, a revalidation study was undertaken to pre-test (using cognitive

interviews15), revise and then reassess the psychometric properties of ELDQOL. The

purpose of this paper is to describe this final phase in the development of the measure

and report its psychometric properties.

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Methods

Qualitative phase

Qualitative (cognitive) interviews were undertaken with 16 parents and 17 health and

other professionals in order to ascertain their opinions on the wording, coverage and

layout of the questionnaire.

The parent participant group comprised 5 couples (the young person’s mother and

father) and 6 mothers. The 11 children of these parents were 8 boys and 3 girls, age

range 18 months to 21 years. Two young people attended residential school, 7

attended special schools or day centres, and one a mainstream school. The parents

were identified by a consultant or senior nurse at 2 specialist hospitals in the north of

England. They were selected because of their child’s condition and because they were

judged to be interested in all aspects of their care.

The professional participant group consisted of 10 consultant paediatric neurologists

or neurologists with a special interest in epilepsy and learning disabilities, one

associated health services researcher, two paediatric epilepsy nurse specialists, two

nurses specialising in epilepsy and learning disabilities, two teachers/play leaders, and

one psychologist.

All participants were sent a copy of the existing ELDQOL questionnaire and asked to

complete it immediately prior to the in-depth interview. Interviews were tape

recorded and lasted approximately one hour. They involved scrutiny of each question

in turn, where participants’ views were sought on interpretation, coverage, content,

wording and scale construction. The tapes were transcribed for analysis.

Psychometric phase

Following revision based on the findings of the cognitive interviews, the final version

of ELDQOL was administered in a postal survey to 47 parents/guardians and 21

formal carers of children with epilepsy and learning disabilities. The parents were

identified by consultant paediatric neurologists and epilepsy specialist nurses at 4 UK

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hospitals, who explained the study and asked whether they would be willing to

complete the questionnaire. Those who agreed were sent a study information sheet

together with a copy of the questionnaire and a consent form and asked to return both

when they had been completed. For the purposes of evaluating test-retest reliability,

parents were sent a second questionnaire approximately 2 weeks after completing the

first. Formal carers were identified through a national long-stay

residential/assessment centre.

The mean age of children recruited to the study was 11.5 years (SD 4.6, range 2 –

191); 58% were male and 42% female. Of the parent respondents, 39 were mothers, 3

were fathers, and 2 were other relatives; 3 of the questionnaires were jointly

completed by both parents.

The final version consisted of 70 items covering seizure severity, seizure-related

injuries, AED side-effects, behaviour, mood, physical functioning, cognitive

functioning, social functioning, parental concern, communication, overall QOL and

overall health. The items covering behaviour, seizure severity, mood and side-effects

domains are summed to create 4 subscales containing 9, 14, 16 and 19 items

respectively. On each subscale, a higher score indicates poorer functioning. The

remaining domains consist of single or several non-summed items. Subscales from

two other outcome measures [the Aberrant Behavior Checklist (ABC)16 and the Child

Health Questionnaire (CHQ)]17 were also administered for the purposes of evaluating

the construct validity of ELDQOL.

In order to evaluate validity, t-tests and correlations were used to examine the

relationship between ELDQOL sub-scales and:

* the Irritability and Hyperactivity subscales of the ABC;

* the Impact on Parental Time, Emotional Impact on Parent, and Family

Activities sub-scales of the CHQ;

* 4 global items (overall health, overall QOL, perceived severity of condition 1 Age was not recorded for 13 children.

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and disability level).

Severity of disability was assessed using a 4-item scale developed by a consultant

paediatric neurologist (RA) with a specialist interest in epilepsy and learning

disability. It covers mobility, feeding, dressing and speech, each item having 5

response options ranging from the worst to the best possible level of functioning.

It was predicted a priori that there would be:

* a significant relationship between the ABC Irritability and Hyperactivity

scales and scores on each ELDQOL subscale;

* a significant relationship between the 3 CHQ scales and scores on each

ELDQOL subscale;

* a significant relationship between overall health and scores on each ELDQOL

subscale;

* A significant relationship between overall QOL and scores on the Side-Effects,

Seizure Severity, and Mood subscales

* A significant relationship between perceived severity of condition and each

subscale

* A significant relationship between disability level and Seizure Severity.

Internal consistency of the 4 sub-scales was assessed using Cronbach’s alpha

coefficients and item-total correlations. Test-retest reliability was assessed using

intraclass correlation coefficients. Floor and ceiling effects for each subscale were

examined.

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Results

Qualitative phase

Views of parents

Six issues were identified through the cognitive interviews with parents: validity of

domains, multiple seizure types, wording, ease of completion, response categories and

identifying change. It was clear that the questionnaire resonated with parents’

experiences and concerns, the questions being described as ‘very good’ and ‘geared to

parents’ for example. However, it did not, in its existing form, take into account that

some children have no mobility or verbal skills. Some commented on the lack of

lifestyle questions to capture social activities and interests. In terms of multiple

seizure types, some parents found it difficult to identify which seizure type they

should refer to in answering the questions. There was a consensus that use of the

word ‘seizure’ was preferable to ‘attack’. The ‘layman’s language’ was appreciated

because it was easy to understand, and the length of the questionnaire was viewed as

good, ‘quick to do’ and ‘easily to fill in’. Instructions were described as ‘clear’,

‘logical’ and ‘concise’. Overall, parents felt that they had sufficient choice in

response categories, and being asked to concentrate on the past 4 weeks seemed

acceptable.

Views of professionals

Interviews with professionals highlighted several broad methodological issues, in

particular the nature of the proxy respondent, scope and objectives of the

questionnaire, sensitivity to change, and questionnaire design. Participants felt

generally that parents would be able to answer the majority of the questions and

would therefore be appropriate proxies. However, there was some reservation

regarding the suitability of nursing, teaching or respite care staff who may not have

known the child for long – ‘it would be necessary to know the child inside out’ to be

able to complete some of the sections of the questionnaire.. In terms of the scope and

objectives of the questionnaire, its orientation led some to query what was being

sought and by whom it would be used. The addition of socially based QOL questions,

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a ‘health profile’ and a section covering function was suggested. In terms of design,

most professionals felt the length of the questionnaire was about right. Some thought

the use of the word ‘attack’ was regressive in terms of practice and preferred the term

‘seizure’.

Revisions made as a result of the qualitative phase

Taking into account the comments from parents and professionals, a number of

revisions were made. In summary:

* the word ‘seizures’ replaced the word ‘attacks’

* ‘can’t say’ and ‘does not apply’ response options were added

* a question about perceived control was dropped because of ambiguity of

meaning; and one about perceived severity was added

* an item was added to those about seizure-related injuries

* an item covering ‘usual activities’ (school, playing, socialising) was added to

the behaviour subscale

* 2 items (‘sociable’ and ‘depressed’) were dropped from the mood subscale and

replaced by three new ones (‘sad’, ‘withdrawn’, ‘cooperative/helpful’)

* 2 items were dropped from the side effects profile (hair loss, dizziness) and 2

were added (weight loss, loss of appetite); and a single item,

‘restlessness/hyperactivity’ was separated into two

* clearer/more detailed instructions were provided (including a statement

instructing parents/proxies to think about the most severe seizures in the case

of multiple seizure types, and emphasising that questions relate to the last four

weeks)

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Psychometric phase

Reliability

As shown in Table 1, internal consistency of the Behaviour, Seizure Severity, Mood

and Side-Effects scales was high (0.74 – 0.95). Item-total correlations exceeded the

desired 0.4 for most items, although in each scale there were some items which did

not meet this: 3/9 items in the Behaviour Scale (‘problems sleeping‘, ‘being prevented

from taking part in normal activities‘, and ‘appetite a problem‘); 7/14 items in the

Seizure Severity scale (‘aware of surroundings after seizure‘, ‘blank out/lose

consciousness‘, ‘fall to the ground‘, ‘soil self‘, ‘injure mouth/cheek /tongue‘, ‘upset

by injuries‘, ‘appear sleepy/subdued‘); 4/16 items in the Mood scale (‘tearful‘,

‘hyperactive‘, ‘withdrawn‘, ‘cooperative‘); and 3/19 items in the Side-effects scale

(‘skin problems‘, ‘shaky hands‘, ‘weight gain.

The test-retest reliability of each subscale was high (range 0.80 - 0.96, Table 1).

Floor/ceiling effects were acceptable in the Side Effects scale, low in the Seizure

Severity scale, and there were none in the Mood or Behaviour scales (Table 1).

Validity

Table 2 shows that all but one of the 4 ELDQOL subscales (Behaviour) were

moderately to highly correlated with both the Irritability and Hyperactivity scales of

the ABC, and that all 4 were moderately to highly correlated with the Emotional

Impact and Family Activities scales of the CHQ. Two of the ELDQOL subscales

(Seizure Severity and Side-effects) correlated moderately with the Impact on Parental

Time scale of the CHQ.

Table 3 shows a significant relationship between mean scores on the Behaviour and

Mood subscales by overall health. There was a similar though non-significant trend

for the Seizure Severity and Side Effects subscales.

As can be seen in Table 4, those with poorer perceived overall QOL tended to have

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higher mean scores on the ELDQOL scales, although these were not statistically

significant.

Mean scores on each of the 4 subscales were significantly worse for parents who felt

their child’s condition was very severe compared to those who felt it was somewhat or

moderately severe (Table 5).

The Seizure Severity and Behaviour subscales were significantly correlated with

severity of disability (Table 6). No significant correlation was found for the Side-

Effects and Mood subscales.

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Discussion

ELDQOL was derived using currently accepted standards for scale development,

including qualitative and cognitive interview techniques with the target groups. The

ongoing involvement of parents and professionals in determining the content and

format of the measure has enhanced its acceptability and ease of completion. The final

version of ELDQOL has very good evidence of reliability and validity, making it a

promising proxy instrument for assessing the QOL of children/young adults with

epilepsy and learning disability. Although in this validation exercise parents were not

asked to note length of time taken to complete ELDQOL, this was previously

estimated as only around 20 minutes5, a factor which may further contribute to its

acceptability.

In terms of internal consistency, each of the 4 subscales had high Cronbach’s alpha

values. For each scale there were some items which did not meet the desired 0.4 level

for item to total scale correlation.19 However, in each case the effect on Cronbach’s

alpha when these items are removed from the scale is negligible or has no effect and

we therefore propose to retain these items on the grounds of

comprehensiveness/content validity.

The test-retest exercise found that each of the 4 subscales achieved ICCs well above

the required level of 0.70 for group comparisons, and 3 of the 4 performed well

enough for comparing individuals over time (0.90).19 Each scale performed well or

perfectly in terms of floor/ceiling effects.

We found excellent evidence of construct validity as all but one of the 4 ELDQOL

subscales (Behaviour) were moderately to highly correlated with both the Irritability

and Hyperactivity scales of the ABC, and all were moderately to highly correlated

with the Emotional Impact and Family Activities scales of the CHQ. Poorer

perceived health was significantly related to poorer mean scores on two of the

ELDQOL subscales, and a similar trend was seen for the remaining two, providing

further evidence of construct validity. Greater perceived severity of the condition was

significantly related to higher scores on each subscale, and disability level was

significantly correlated with scores on the Seizure Severity and Behaviour scales.

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Although the sample size was relatively small we would suggest that, based on both

psychometric analysis and feedback from parents, ELDQOL will be a valuable

contribution to outcomes measurement in childhood epilepsy and learning disability,

particularly in the context of treatment trials, but also, with the addition of new items

to address parent and professional concerns over coverage and content validity, in a

wider research context. Further studies are needed to assess its responsiveness to

change.

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Table 1 Reliability and floor/ceiling effects of the 4 ELDQOL subscales

ELDQOL Su

bscale

Cronbach’s

alpha

Item-total co

rrelations

Intraclass

correlation

(test-retest)

Floor / ceilin

g effects (%)

Behaviour 0.79 .24 - .70 0.80 0 / 0

Seizure Sever

ity

0.74 .19 - .54 0.96 2 / 0

Mood 0.86 .21 - .78 0.91 0 / 0

Side-effects 0.95 .33 - .88 0.92 10 / 0

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Table 2 Validity: correlation between the 4 ELDQOL sub-scales and ABC

and GHQ sub-scales1

ELDQOL

subscale:

ABC subscales CHQ subscales

Irritability Hyperactivity Impact on

Parental

Time

Emotional

Impact on

Parent

Family

Activities

Behaviour r=0.008

p=0.95

r=0.13

p=0.32

r=0.25

p=0.1

r=-0.42

p<0.01

r=-0.31

p<0.05

Seizure

Severity

r=0.29

p<0.05

r=0.38

p<0.01

r=-0.33

p<0.05

r=-0.47

p<0.01

r=-0.48

p<0.01

Mood r=0.74

p<0.001

r=0.56

p<0.001

r=-0.28

p=0.06

r=-0.48

p<0.01

r=-0.63

p<0.001

Side-effects r=0.38

p<0.02

r=0.39

p=0.01

r=-0.43

p<0.01

r=-0.54

p<0.001

r=-0.47

p<0.01

1 Pearson’s correlation coefficient

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Table 3 Validity: mean scores of the 4 ELDQOL subscales by overall

health

Overall health:

Very good/g

ood

Fair/poor/v po

or

t test p value

Seizure severity 26 31 -1.8 0.08

Side-effects Profi

le

30 37 -1.9 0.06

Behaviour Scale 17 21 -3.6 0.001

Mood 32 35 -2.1 0.038

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Table 4 Validity: mean scores of the 4 ELDQOL subscales by overall QOL

Overall QOL:

Very god/go

od

Fair/poor/v po

or

t test P value

Seizure severity 29 30 -0.2 0.81

Side-effects Profi

le

30 36 -1.4 0.16

Behaviour Scale 17 19 -1.8 0.078

Mood 32 35 -1.8 0.071

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Table 5 Validity: mean scores of the 4 ELDQOL subscales by perceived

severity of condition

How severe:

Very Somewhat/moderate/

Mild

t test p value

Seizure severity 35 24 4.3 <.001

Side-effects

Profile

43 32 2.9 <0.01

Behaviour Scale 21 17 3.1 <.01

Mood 37 31 2.4 <.03

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Table 6 Validity: correlation between ELDQOL subscales and disability

level

Scale Pearson’s r p value

Seizure severity -0.43 .001

Side Effects Profile 0.02 .93

Behaviour scale 0.44 .000

Mood -0.1 .41

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Acknowledgements

We would like to thank all the parents who helped us at the various stages of this

study; and the health professionals who contributed to the revalidation exercise. Our

sincere thanks go to: Drs Tim Betts, Lynda Brook, Richard Newton, Rosemary

Newton, William Whitehouse and Chris Verity; to epilepsy specialist nurses, Lynne

Clack and Gerry Litherland; and to Helen Donovan, for their help with identifying

potential study participants. The study was funded by GSK in its various incarnations,

to whom we also extend our thanks.

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